DE102022213832A1 - Measuring device for measuring forces acting on a vehicle combination and method for operating the same - Google Patents

Abstract

The invention relates to a measuring device (10a, 10b) for measuring forces acting on a vehicle combination (1), the vehicle combination (1) consisting of a towing vehicle, tractor (2) or a tractor with a coupling device (6) and a trailer (3) coupled thereto or an attachment coupled thereto. According to the invention, a fiber-optic sensor (11) is arranged on the housing (7) of a vehicle transmission (4) of the towing vehicle, tractor (2) or tractor in such a way that it also deforms when the housing (7) of the vehicle transmission (4) is mechanically deformed and in the process changes its optical properties, that the sensor (11) has an optoelectronic control unit (12) for generating and processing an optical output signal (20, 22), that a computer program is stored in the control unit, by means of which a force acting on the coupling device (6) can be determined by evaluating the optical output signal (20, 22). Coupling force can be determined, and that by means of the control unit (12) an electrical signal representing the measured coupling force can be generated and sent to a vehicle control unit (29).

Description

The invention relates to a measuring device for measuring forces acting on a vehicle combination, the vehicle combination consisting of a towing vehicle with a coupling device and a trailer vehicle coupled thereto or an attachment coupled thereto. The invention also relates to a method for measuring coupling forces and/or axle loads with such a measuring device, a computer program for determining coupling forces and/or axle loads, and a vehicle combination with such a measuring device.

The dynamic behavior of vehicle combinations, such as agricultural tractors with trailers or attachments coupled to them, is significantly influenced by the controlled and/or independent movements of the trailer or attachment and the resulting tensile, shear and transverse forces as well as axle loads. Therefore, the most accurate possible knowledge of the current coupling forces and axle loads on their trailers or vehicle axles is an important prerequisite for ensuring the safe and efficient operation of such a vehicle combination.

Measuring devices for measuring coupling forces and/or axle loads on such vehicle combinations are known in various designs. Conventional and already frequently used force sensors use strain gauges or piezo elements. Such arrangements of force sensors are usually attached to an additional component that is clamped into a coupling device.

From the EN 10 2018 106 855 A1 Such a measuring device for measuring forces and/or moments between a motorized vehicle and a trailer or attachment that is towed or pushed by it is known. This measuring device is arranged in a coupling area between the motorized vehicle and the towed or pushed trailer or attachment. It has a cross-shaped carrier with four radially extending measuring arms, which is arranged transversely to an imaginary longitudinal axis of the motorized vehicle. The carrier is clamped between a base plate and a standard coupling carrier. Four sensor elements are arranged on the four measuring arms of the carrier, for example four strain gauges that serve as force sensors. The sensor elements are connected to an electronic evaluation device, which can use known algorithms to calculate the magnitude and direction of the forces and moments acting on the measuring device from the signals of the sensor elements and forward them to a driving condition management system.

The EN 10 2019 124 281 A1 shows a fifth wheel coupling with a coupling plate for receiving a kingpin of a semi-trailer vehicle, in which the coupling plate is connected to a bearing block via a bearing insert for pivoting storage. An intermediate element is arranged between the bearing insert and the coupling plate, which has a force sensor in the form of a strain gauge or a piezo element. A force flow that acts on the coupling plate is transmitted to the bearing block via the intermediate element.

In addition, optical sensors are known in which light beams are used to measure geometric dimensions on load-bearing components of vehicle combinations.

From the EP 2 366 563 A2 For example, a trailer coupling for a passenger car with such a sensor arrangement with at least one light source, such as an infrared LED, and with at least one optical sensor is known. To measure an angular position of a towing coupling of a trailer vehicle relative to a carrier of a spherical coupling body of the trailer coupling, onto which a receiving device of the towing coupling can be placed, the light of the light source is directed at the towing coupling when the vehicle is coupled and the reflected light is detected by the optical sensor. An angular position can be determined from the measurement signal of the optical sensor.

Fiber optic sensors are also known. Such sensors have a light source, a light detector and an optical waveguide, whereby in so-called intrinsic systems the optical waveguide itself acts as a sensor. External influences such as temperature fluctuations or mechanical loads such as stretching or vibrations influence the light signal transmitted in the optical waveguide. Various parameters can be used to evaluate the measured light conduction in the optical waveguide, which can occur when the light interacts with the material of the optical waveguide, such as inelastic light scattering, elastic light scattering or light interference. It is known to use such fiber optic sensors to test and monitor infrastructure facilities such as fiber optic networks, bridges or pipelines.

For the area of automotive engineering, the EP 1 421 355 B1 an arrangement of several force sensors on a wheel bearing of a vehicle wheel is known. This arrangement is used to determine forces and moments acting on a wheel suspension of the vehicle wheel. The force sensors mentioned form a structural unit with a speed sensor. The force sensors can be, for example, fiber optic compressive stress elements. These fiber optic compressive stress elements are not described in more detail in this publication.

Against this background, the invention was based on the task of presenting a measuring device for measuring coupling forces and/or axle loads on a vehicle combination, which is easy and inexpensive to manufacture, is insensitive to dirt, and can be used variably in terms of its installation position. This measuring device should be particularly suitable for use on an agricultural, forestry or construction vehicle combination for measuring the coupling force between a towing vehicle, tractor or tractor unit and a trailer or attachment. This measuring device should also be usable for measuring the axle load on a rear axle of the vehicle loaded by a trailer or attachment. Finally, a method should be presented with which such a measuring device can be operated in accordance with the task.

The solution to the device-related problem is achieved with a measuring device which has the features of the two independent device claims. An independent method claim defines the method steps for solving the method-related problem. Advantageous embodiments and further developments are mentioned in the respective associated dependent claims.

The invention is based on a first idea, according to which the coupling forces acting on the coupling device of a vehicle do not necessarily have to be determined on the coupling device itself, but that this is also possible on vehicle components which, like the coupling device, are attached or mounted on load-bearing components of the vehicle. This works because the forces acting on the coupling device are indirectly transferred to the vehicle components mentioned via load-bearing frame components of the vehicle. Such a measuring location can be, for example, the housing of a vehicle transmission or a component of a vehicle wheel axle, which are connected to the coupling device of the vehicle via load-bearing frame components of the vehicle. Based on this, the invention was based on a second idea that the coupling forces mentioned can be determined at the locations described advantageously using a fiber optic measuring device.

The invention therefore relates to a measuring device for measuring forces acting on a vehicle combination, wherein the vehicle combination consists of a towing vehicle, tractor or tractor unit with a coupling device and a trailer vehicle coupled thereto or an attachment coupled thereto.

To solve the device-related problem, according to a first variant defined in independent claim 1,
that a fibre optic sensor is arranged on the housing of a vehicle transmission of the towing vehicle, tractor or tractor unit in such a way that
that if the housing of the vehicle transmission is mechanically deformed, it also deforms and changes its optical properties,
that the sensor has an optoelectronic control unit for generating and processing an optical output signal,
that a computer program is stored in the control unit,
by means of which a coupling force acting on the coupling device can be determined by evaluating the optical output signal,
and that an electrical signal representing the measured coupling force can be generated by means of the control unit and sent to a vehicle control unit.

According to this first solution variant, the coupling force acting on the coupling device is determined indirectly by a fiber optic measurement of the deformation of the gearbox housing of the towing vehicle, tractor or tractor unit. This is possible because the gearbox housing of the towing vehicle bends slightly due to a coupling force acting on the coupling device of the tractor unit, which can be measured using the measuring device.

The measuring device defined in independent claim 2 also serves to measure forces acting on a vehicle combination,
whereby the vehicle combination also consists of a towing vehicle, tractor or tractor with a coupling device and a trailer or attachment coupled thereto. This second variant of the measuring device is characterized by
that a fibre optic sensor is mounted on at least one axle trumpet of a vehicle wheel axle of the towing vehicle, tractor or tractor unit in such a way is arranged,
that this deforms when the axle trumpet is mechanically deformed and thereby changes its optical properties,
that the sensor has an optoelectronic control unit for generating and processing an optical output signal,
that a computer program is stored in the control unit,
by means of which a coupling force acting on the coupling device can be determined by evaluating the optical output signal,
and that an electrical signal representing the measured coupling force can be generated by means of the control unit and sent to a vehicle control unit.

In this second solution variant, the coupling force acting on the coupling device is also determined indirectly, namely by a fiber optic measurement of the deformation of at least one axle trumpet of a vehicle wheel axle of the towing vehicle, tractor or tractor unit. This is possible because a coupling force acting on the coupling device of the tractor unit is partially transferred to the vehicle axle and its axle trumpets via load-bearing frame components of the vehicle. These forces bend the axle trumpets, which can be measured using the measuring device. The measuring devices according to the two described invention variants therefore only differ in the mounting location of the fiber optic sensor.

The rear wheel axle of the tractor or towing vehicle is preferred for arranging the measuring device because it is particularly close to a coupling device that is usually arranged at the rear of this vehicle. In the case of a coupling device for an attachment that can be coupled to the front of the towing vehicle, the measuring device can also be attached to a frame component of the vehicle that is arranged there and with which a coupling force can be transmitted.

By means of the measuring device according to the second solution variant, the axle load acting on the rear axle of the tractor or the towing vehicle, which may be load-dependent, can also be determined with less computational effort.

With regard to the internal structure of the measuring device, according to a further development of the invention,
that the fiber optic sensor has at least one optical fiber connected to the optoelectronic control unit,
that the control unit has a light source and a light detector,
that the light source is designed and arranged to emit a light signal propagating in the optical waveguide,
and that the light detector is designed to detect and convert optical-electrical signals from a light reflected back into the light detector via the optical waveguide,
or one transmitted through the optical fiber,
or an output signal of the light signal fed to the light detector via an additional optical signal line.

The measuring device according to the invention therefore has a fiber optic sensor with an optical waveguide. In common parlance, the term optical waveguide is often used as a synonym for optical fiber. Due to their small cross-section, optical waveguides can easily be placed on or inside an existing vehicle component. Optical waveguides can be bent relatively flexibly so that they can be arranged in lines, loops or spatial curves. Fiber optic sensors are also insensitive to electromagnetic interference and corrosion-resistant.

Although the description of the invention focuses on an agricultural combination with a tractor and a trailer or attachment coupled to it with its usual areas of use on and off roads, the measuring device with the features of the invention is not limited to this. The measuring device can in principle be used advantageously on all types of vehicle combinations on which coupling forces and/or axle loads are to be measured.

According to the first variant mentioned, it can be provided that the fiber optic sensor is arranged on a rear end area of a gearbox housing of the towing vehicle, located between the towing vehicle, tractor or tractor unit and the trailer or attachment. This arrangement of the fiber optic sensor of the measuring device enables the coupling forces to be recorded. By arranging the fiber optic sensor on or inside the gearbox housing, the manufacturing costs can be reduced and installation space for arranging the measuring device on a coupling device can be saved. In particular, no separate supports, intermediate plates or the like are required, which would form a coupling on the outside of the vehicle body for the coupling force measurement on a trailer bracket or the like. In addition, the fiber optic sensor inside the gearbox housing is protected from harmful external environmental influences in the rough everyday operation of an agricultural vehicle, such as the ingress of moisture and/or dirt particles. This increases the damage-free service life of the measuring device.

According to the second variant of the invention, it is provided that the fiber optic sensor is arranged within one or two axle trumpets of a rear vehicle wheel axle of the towing vehicle. The arrangement of the fiber optic sensor of the measuring device within one or both axle trumpets of a rear axle of the towing vehicle, tractor or tractor unit enables a direct measurement of the axle load on the rear axle, which is particularly stressed during operation of the agricultural combination. The value of the coupling force acting on the coupling device of the towing vehicle can then be calculated from the determined value of the axle load.

The two variants mentioned can be advantageously combined with one another. For this purpose, a continuous optical fiber can be laid in the rear end area of a gearbox housing and further into the axle trumpets of the rear axle. Alternatively, two fiber optic sensors can be present in the measuring device, i.e. a first fiber optic sensor in the end area of the gearbox housing and a second fiber optic sensor in the two axle trumpets. In any case, a spatially resolved recording of the forces and moments acting is possible. The spatial resolution of the measured values determined by the measuring device will be explained later.

The measuring device according to the invention uses a so-called intrinsic fiber optic sensor. The optical fiber itself acts as a sensor that is suitable for detecting various physical parameters such as temperature, pressure and strain. The parameter to be detected modulates various properties of the light, such as its intensity, phase, wavelength and/or polarization. Based on the basic principle of light propagation in an optical fiber, the light propagation changes when the optical fiber is exposed to changes in environmental conditions such as temperature, pressure and/or strain. The measuring device according to the invention therefore uses the ability of an optical fiber to change its light-conducting properties when external forces act on the optical fiber. Such forces generate in particular mechanical strains, such as those that occur on a coupling device of a vehicle combination and vehicle components downstream of this coupling device. The optical fiber is arranged and attached to a surface of a transmission housing in such a way that coupling forces that act on a coupling device of the tractor or towing vehicle can be measured if a trailer or an attachment is coupled there.

According to the invention, the coupling forces acting on a coupling device of the towing vehicle can also be determined from the axle load acting on a rear axle of the tractor or the tractor or the towing vehicle. For this purpose, a measuring device according to the invention is attached to at least one axle trumpet of the rear axle or to another axle component of the rear axle close to the axle. The coupling forces acting on a coupling device of the vehicle can then be calculated from the axle load forces measured by the measuring device.

An optical waveguide for fiber optic measurements usually consists of a cylindrical conductor for the propagation of optical waves, which has a thin core radially inside and a hollow cylindrical jacket surrounding it. The core and jacket are usually made of quartz glass. However, they differ in their refractive index. The jacket of an optical waveguide is often provided with an outer protective layer made of plastic. A fiber optic cable has several optical waveguides combined to form a fiber bundle. The optical waveguides can have an additional jacket for installation in a harsh or chemically aggressive environment.

A distinction is made between single-mode fibers and multi-mode fibers in optical fibers. Single-mode fibers have a very small core diameter in which the light can propagate in only one basic mode, resulting in a homogeneous beam profile. Multi-mode fibers have a larger core diameter, which allows the propagation of a large number of light modes, resulting in a highly structured beam profile. Depending on the application, required signal strength, length of the sensor, spatial resolution of the measurement, etc., a single-mode fiber or a multi-mode fiber can be advantageous. In order to keep the light energy in the core, the refractive index of the core must be greater than that of the cladding. In order to achieve a high refractive index, the fiber core is often doped with a semiconductor material or a semi-metal, such as germanium. The light signal propagating in the forward direction in the core of the optical fiber is at least predominantly totally reflected by the core cladding, so that a sufficiently strong output for analysis is achieved. output signal or backscatter signal is present.

The measurement of a spectrum of the output signal of the optical fiber can be carried out spatially resolved at a single measuring point or with several discretely distributed point-like measuring points. If the measuring points are arranged very close to one another, this is referred to as a quasi-continuous measurement. In this context, a distributed measurement means that the measurement is not carried out at one point, but rather over the entire length of the optical fiber.

The output signal usually contains various types of light scattering, which can be evaluated to determine an external influence on the sensory optical fiber, such as a force and/or moment effect, for example a strain. To evaluate a scattered output signal that is then recorded by the light detector, methods are used that use different measurement signals that result from the interaction of the light signal with the optical fiber. A detailed description of known fiber optic sensor technologies is known, for example, from the following publication by Andreas Künzel: Parameter identification based on fiber optic measured quasi-continuous strain signals, Berlin, Technical University, dissertation, 2016.

To describe the mode of operation of the present invention, the following overview of methods of spectral analysis which are suitable for evaluation for the purpose of the invention, namely for the determination of coupling forces and axle loads, as well as in a further development of the invention for the determination of vibrations and/or temperatures which influence the coupling forces and axle loads on a towing vehicle, is sufficient.

The 5 shows a well-known scheme of light scattering in an optical waveguide, which is presented in the above-cited publication by Andreas Künzel. In it, the scattering intensities I for Rayleigh scattering, Raman scattering and Brillouin scattering are plotted against the wavelength λ. The wavelength λ of the Rayleigh scattering is clearly not shifted in comparison with the wavelength λ_0 of the incident light signal. The scattering intensity I of the Rayleigh scattering signal is not dependent on the temperature T or the strain ε.

It should be noted here that the strain ε of a solid is defined as the ratio of its change in length to its original length.

Unlike Rayleigh scattering, Raman scattering exhibits a so-called Stokes wavelength shift or an anti-Stokes wavelength shift. The scattering signal intensity I of Raman scattering depends only on the temperature T of the measuring body, i.e. on the temperature T of the optical fiber. Brillouin scattering also exhibits a Stokes wavelength shift or an anti-Stokes wavelength shift, but the size of the shift depends on both the temperature T and the strain ε.

In addition, interference patterns can be generated by the light beam, which occur due to the nature of the optical waveguide or are deliberately brought about by appropriate preparation of the same. By analyzing such an interference pattern, it is also possible to obtain information about a change in the elongation ε of an optical waveguide. The individual types of light scattering and the interference of light are explained in more detail using several embodiments of the invention.

According to one embodiment of the invention, it is provided that the fiber optic sensor has the functionality of a fiber Bragg grating sensor, wherein at least two fiber Bragg gratings are arranged in the optical waveguide.

In a fiber Bragg grating sensor, several gratings that modulate the refractive index are inscribed in the optical waveguide at defined intervals, for example by irradiation with UV light. Typical grating lengths are ten millimeters, with the period of the grating planes in the range of a few hundred nanometers. The grating planes act as interference filters that reflect and/or transmit a certain part of the incident light spectrum, the frequency of which depends directly on the period of the spacing of the grating planes. Thus, light of a certain wavelength is reflected and/or transmitted per grating from the input light power of the light source. By stretching the optical waveguide in the area of the grating, the period of the grating spacing changes, which changes the wavelength of the reflected and/or transmitted light. This can be used to obtain the desired information about the stretching state of the optical waveguide or its change.

Accordingly, an optical fiber attached to the gearbox housing or to the axle trumpets of a rear axle of a tractor or towing vehicle attached, each of these fiber Bragg gratings at a distance of, for example, several centimeters. This provides a corresponding number of measuring points, which results in a certain spatial resolution of a measurement to be carried out. Because the coupling forces acting on the coupling device of the towing vehicle are at least partially transmitted to the transmission housing and the rear axle of the towing vehicle, the coupling force on the coupling device can be deduced using the forces measured there.

The evaluation of the reflected and/or transmitted light spectrum after interference with the fiber Bragg gratings is carried out using the light detector mentioned. Very short measurement cycles are possible with a pulsed light source. Designing the optoelectronic sensor as a fiber Bragg grating sensor is therefore advantageous for detecting dynamic changes in the coupling forces, as they typically occur during operation of a vehicle combination.

According to a further embodiment of the invention, it is provided that the fiber optic sensor of the measuring device has the functionality of a Raman sensor.

The Raman effect is the backscattering of light with a shift in the reflection wavelength of a scattered light signal compared to the excitation wavelength of an incident light signal as a result of inelastic scattering of light by thermal molecular vibrations of molecules. Accordingly, in a Raman sensor with distributed temperature measurement, the backscattered light in an optical waveguide is subject to the Stokes shift mentioned above. In Raman scattering, the backscattered light consists of a Stokes component and an anti-Stokes component, as shown in the 5 is shown. If a photon of light coupled into an optical waveguide hits a scattering molecule in the material of the optical waveguide, energy is transferred from the photon to the scattering molecule in the Stokes component, and the energy and frequency of the backscattering are lower, i.e. the wavelength is longer, than that of the excitation. In the anti-Stokes component, energy is transferred from the scattering molecule to the photon. The energy and frequency of the backscattering are correspondingly higher, i.e. the wavelength is shorter. The intensity of the Stokes component is not dependent on the temperature, but the intensity of the anti-Stokes component is strongly dependent on the temperature. By comparing the two Raman peak intensities, the temperature in the optical waveguide can be calculated. The location information is calculated from the travel time of the light waves in the optical waveguide.

Raman scattering is insensitive to mechanical strain and the spatial resolution is rather low. However, temperature fluctuations in the optical fiber can be determined very precisely. This additional information makes it possible to calculate the temperature component when determining strains in the optical fiber, which can result from both the effect of coupling forces and temperature changes. For example, a second optical fiber can be laid parallel to the first optical fiber in the structure of the fiber optic sensor. This ultimately increases the accuracy when determining the coupling forces.

According to another embodiment of the invention, the fiber optic sensor of the measuring device has the functionality of a Brillouin sensor.

Accordingly, in a Brillouin sensor with distributed temperature and strain measurement, the backscattering results from the interaction between the light waves coupled into the optical waveguide and acoustic lattice vibrations of the molecular lattice, so-called phonons, in the material of the optical waveguide. Their properties depend linearly on the density of the material of the optical waveguide via the speed of sound, which is changed at least approximately linearly by a strain. Mechanical and/or thermal strains of the optical waveguide lead to a proportional shift in the wavelength of both the Stokes component and the anti-Stokes component in the opposite direction, as shown by the 5 shows. Brillouin scattering is therefore sensitive to strain. However, Brillouin scattering cannot distinguish between mechanical and thermal strain. In applications where hardly any temperature fluctuations are to be expected, coupling forces can still be determined with sufficient accuracy using this method.

According to a further embodiment of the invention, it is provided that the fiber optic sensor of the measuring device has the functionality of a Rayleigh sensor.

The occurrence of scattered light with unchanged wavelength is called Rayleigh scattering. Rayleigh scattering is based on the predominantly elastic scattering of a light signal by molecules. In optical fibers, it occurs as a result of inhomogeneities in the fiber core, which are due to unwanted or targeted inclusions. and/or density fluctuations of the material. The strength of the scattering, i.e. the scattering angle of the beam deflection, depends on the frequency of the emitted light signal. The scattered signal does not show a wavelength shift to the emitted light signal, which in 5 This type of interaction is not or at most only slightly dependent on the strain and temperature state of the optical fiber, but is sensitive to vibrations and sound impulses that act on the optical fiber. Rayleigh backscatter signals are therefore suitable as an additional source of information for identifying vibrations that are transmitted via the vehicle bodies. Such vibrations can occur in connection with coupling forces, for example due to anomalies in the body and/or in the coupling device during operation.

For the sake of completeness, interferometric measuring methods should also be mentioned. These methods examine the phase shift of two crossed, superimposed light waves. If a change in the path of an optical signal reflected from the measuring object, i.e. the optical waveguide acting as a sensor, caused by a physical load such as stretching, vibration or thermal stress, is superimposed with a constant reference signal, the deformation or deflection can be determined from an interference pattern. Such a setup with two crossed light signals is basically possible for installation in a gearbox or in an axle trumpet, but is rather complex and therefore not intended here.

As described at the outset, the invention also relates to a method for measuring coupling forces and/or axle loads on a vehicle combination consisting of a tractor or towing vehicle and a trailer vehicle coupled thereto or an attachment coupled thereto, wherein a measuring device is used which has the already described features of at least one of the device claims.

To solve the procedural task, it is planned
that an output signal received by the light detector is evaluated by the optoelectronic control unit continuously or repeatedly at time intervals by means of a spectral pattern comparison between light signal parameters emitted by the light source and detected by the light detector,
where the intensity, phase, wavelength and/or polarization of the light are used as light signal parameters,
that the degree of deformation of the optical fiber is determined by evaluating the output signal,
that a value of a coupling force and/or axle load causing the deformation of the optical fiber is calculated using a numerical calculation method, and that the calculated coupling force value and/or axle load value is made available as a sensor signal for further processing.

The light source used in a fiber optic sensor is usually a light-emitting diode or a laser diode, depending on the intended evaluation method. Such a light source can emit pulsed light of a single wavelength or with multiple wavelengths in a specific spectrum, such as ultraviolet light (UV light) or infrared light (IR light), at short clock frequencies. This enables time-resolved measurements and/or time-integrated measurements. A light pulse from the light source that is scattered and/or interfered with after an external influence will have different properties in the optical fiber than a previous light pulse before the external influence that led to a change in the stretching, bending or other deformation of the optical fiber.

First, the received output signal can be evaluated by the optoelectronic control unit by a so-called spectral pattern comparison between emitted, reflected and received light parameters, such as intensity, phase, wavelength and/or polarization. These light parameters can be determined by known spectroscopic analyses of the phase, intensity, wavelength and frequency changes as already described. A force-induced deformation of the optical fiber can be determined from the change in the output signal with regard to one or more of the aforementioned parameters due to the application of a force. In addition, information about temperature changes and, if applicable, vibration influences on the optical fiber can be obtained.

Using a numerical calculation method, such as the well-known mathematical method of finite elements (FEM), the causal coupling force or axle load can be reconstructed. In other words, the optical fiber can be used in particular as a force sensor to reconstruct the force-induced deformation of solid bodies, coupling forces and axle loads on the vehicle combination by analyzing a light signal scattered in the optical fiber and on the basis of the FEM analysis. With a suitable arrangement of one or more fiber optic sensors, an algorithm in the optoelectronic control unit can finally be used to determine the force-induced deformation of solid bodies, coupling forces and axle loads on the vehicle combination from the analysis of the material. The output signal of the light signal that has interacted with the optical fiber and is recorded by the light detector can be used to calculate tensile forces, shear forces, transverse forces and/or axle loads, i.e. the force components and moments acting on the vehicle/trailer combination in all three spatial directions.

The coupling force information provided as a sensor signal for further processing can be used, for example, for drive control or brake control and/or for determining the weight of the vehicle combination. A wireless or wired connection to a control unit of the vehicle combination can be set up for this purpose. The information obtained can be used to improve efficient and at the same time safe driving. It is advantageous if this process is carried out continuously while the vehicle combination is in operation. This ensures permanent monitoring of the coupling connection or the axle loads of the vehicle combination.

The invention also relates to a computer program for determining coupling forces and/or axle loads on a vehicle combination consisting of a tractor or a tractor unit or a towing vehicle and a trailer vehicle coupled thereto or an attachment coupled thereto, wherein the computer program is designed in such a way that the said method can be operated with it in accordance with the method claim. The computer program can be an inherent component of the optoelectronic control unit or at least be present in a control device which is functionally connected to the optoelectronic control unit.

Finally, a vehicle combination is claimed, comprising an agricultural tractor, a tractor or a towing vehicle with an attachment and/or at least one trailer vehicle, with a measuring device which is constructed according to at least one of the device claims and is operable to carry out a method according to the independent method claim.

• 1 eine Fahrzeugkombination mit einem Traktor und einem daran angekoppelten Anhängefahrzeug sowie mit einer Messeinrichtung gemäß der Erfindung,
• 2 ein Fahrzeuggetriebe des Traktors gemäß 1, mit beidseitig davon abgehenden Achstrompeten einer Hinterachse, und mit einem endseitig an dem Fahrzeuggetriebe befestigten faseroptischen Sensor zur Messung von Koppelkräften zwischen dem Traktor und dem Anhängefahrzeug gemäß einer ersten Ausführungsform,
• 2a eine vergrößerte Detailansicht des faseroptischen Sensors gemäß 2,
• 3 das Fahrzeuggetriebe mit den Achstrompeten gemäß 1, jedoch mit einem in den Achstrompeten eingebauten faseroptischen Sensor gemäß einer zweiten Ausführungsform,
• 3a eine vergrößerte Detailansicht des faseroptischen Sensors gemäß 3,
• 4 ein vereinfachtes Schema eines faseroptischen Sensors mit einem Faser-Bragg-Gitter,
• 4a ein homogenes Eingangsspektrum eines in einem Lichtwellenleiter des faseroptischen Sensors eingestrahlten Lichtsignals,
• 4b das Transmissionsspektrum eines durch das Faser-Bragg-Gitter des Lichtwellenleiters geleiteten Lichtsignals,
• 4c ein Reflexionsspektrum eines an dem Faser-Bragg-Gitter des Lichtwellenleiters reflektierten Lichtsignals, und
• 5 ein Schema der Stokes-Verschiebung eines Lichtsignals bei der Rückstreuung in einem Lichtwellenleiter, mit Anteilen von Streuintensitäten von Rayleigh-Streuung, Raman-Streuung und Brillouin-Streuung.

The invention is explained in more detail below with reference to embodiments shown in the accompanying drawing. The drawing shows

• 1 a vehicle combination with a tractor and a trailer coupled to it and with a measuring device according to the invention,
• 2 a vehicle transmission of the tractor according to 1 , with axle trumpets of a rear axle extending from both sides thereof, and with a fibre optic sensor attached to the end of the vehicle transmission for measuring coupling forces between the tractor and the trailer vehicle according to a first embodiment,
• 2a an enlarged detailed view of the fiber optic sensor according to 2 ,
• 3 the vehicle transmission with the axle trumpets according to 1 , but with a fibre optic sensor built into the axle trumpets according to a second embodiment,
• 3a an enlarged detailed view of the fiber optic sensor according to 3 ,
• 4 a simplified scheme of a fiber optic sensor with a fiber Bragg grating,
• 4a a homogeneous input spectrum of a light signal radiated into an optical waveguide of the fiber optic sensor,
• 4b the transmission spectrum of a light signal passed through the fiber Bragg grating of the optical waveguide,
• 4c a reflection spectrum of a light signal reflected from the fiber Bragg grating of the optical waveguide, and
• 5 a scheme of the Stokes shift of a light signal during backscattering in an optical waveguide, with contributions of scattering intensities from Rayleigh scattering, Raman scattering and Brillouin scattering.

Some components in the figures are identical and are therefore designated with the same reference numbers. The scheme of the Stokes shift of a light signal during backscattering in an optical waveguide, with proportions of scattering intensities from Rayleigh, Raman and Brillouin scattering according to 5 has already been explained in detail.

In the 1 The agricultural vehicle combination 1 shown consists of a tractor 2 and a trailer 3 coupled to it. The tractor 2 has a vehicle transmission 4 of a known type, which forms a structural unit with a rear axle 5 of the tractor 2. The two vehicles 2, 3 are connected to one another by means of a known coupling device 6 (not shown in detail), for example by means of a bolt coupling. The three spatial components Fx, Fy, Fz of a coupling force act on a coupling device 6 of the tractor 2. The first force component Fx of the coupling force acts in the longitudinal direction of an imaginary longitudinal axis of the vehicle combination 1, which corresponds to a tractive force or a thrust force. The second force component Fy of the coupling force corresponds to a vertical force which, as a resulting axle load, also acts on the rear axle of the tractor 2 at the coupling device 6. The third force component Fz corresponds to a transverse force which acts laterally on the coupling device 6. The coupling device 6 is indirectly connected to the rear axle 5 and the housing of the transmission 4 via frame components of the tractor 2.

The vehicle combination 1 has a measuring device 10a, 10b having the features of the invention for measuring coupling forces and/or axle loads, which is arranged and fastened to the housing of the vehicle transmission 4 or to the rear axle 5 of the tractor 2. The measuring device 10a, 10b is described in more detail below.

As the 2 As illustrated, a first embodiment of the measuring device 10a has a fiber optic sensor 11. This sensor 11 is attached to a trailer-side end of the housing 7 of the vehicle transmission 4 and is located between the rear axle 5 of the tractor 2 and its coupling device 6.

The fiber optic sensor 11 has an optoelectronic control unit 12 and an optical fiber 15. As the enlarged view according to 2a shows, the optical waveguide 15 starts from the optoelectronic control unit 12, is attached to the outside of the gear housing 7 and is led back with its end to the optoelectronic control unit 12 and connected to it. The optical waveguide 15 can be laid in waves, loops or curves with orientation predominantly in one spatial direction or in two or all three spatial directions. This is shown in the 2a merely hinted at.

It is important that the optical waveguide 15 is arranged and attached to the vehicle transmission 4 in such a way that reversible deformations and re-deformations of the transmission housing 7, as typically generated during operation of the vehicle combination 1, are mechanically transferred to the optical waveguide 15 so that it undergoes a corresponding deformation. Such external influences change the properties described at the beginning in the optical waveguide 15 with regard to the light propagation, with individual properties reacting to various external influences, such as expansion, temperature changes, shocks and vibrations, with varying degrees of sensitivity and selectively or cumulatively.

In addition, the 2 two axle trumpets 5a, 5b of the rear axle 5 of the tractor 2, which extend on both sides from the vehicle transmission 4 to rear wheels of the tractor 2 (not shown there). This first fiber optic sensor 11 is provided in particular for detecting coupling forces near the coupling device 6.

In this embodiment, the measuring device 10a includes a sensor line 28 leading to a vehicle control unit 29 and at least one electrical line 31 leading to a power supply source 30.

The 3 and 3a show a second embodiment of a measuring device 10b having the features of the invention, which also has a fiber optic sensor 25 with an optical waveguide 26 and an optoelectronic control unit 27. This second measuring device 10b also includes a sensor line 28 leading to a vehicle control unit 29 and at least one electrical line 31 leading to a power supply source 30.

The second fiber optic sensor 25 is arranged in the two axle trumpets 5a, 5b and attached to their inner wall. It extends over almost the entire length of the two axle trumpets 5a, 5b and through the vehicle transmission 4. This second fiber optic sensor 25 enables the detection of coupling forces that act from the coupling device 6 via the axle trumpets 5a, 5b on the rear axle 5 of the towing vehicle 2. The second fiber optic sensor 25 reacts particularly sensitively to high axle loads on the rear axle 5, which can often occur when operating an agricultural vehicle.

The 4 shows a simplified schematic of the exemplary structure of the fiber optic sensor 11, 25 according to 2a or 3a Accordingly, the optoelectronic control unit 12, 27 has a light source 13 and a light detector 14. The control unit 12, 27 is supplied with electrical energy from the energy supply source 30 via the electrical line 31. In addition, the control unit 12, 27 is connected to the vehicle control unit 29 via the sensor line 28. The light source 13 can be, for example, a light-emitting diode or a laser diode, while the light detector 14 consists, for example, of an arrangement of one or more photodiodes or phototransistors. The light source 13 and the light detector 14 are connected to one another in terms of signals by an optocoupler 16. In addition, the optoelectronic control unit 12, 27 has means (not shown) for optoelectronic signal conversion and computer means for evaluating the received signals in accordance with the method.

The cylindrical optical waveguide 15, 26 has an inner fiber core 17, which is surrounded by an outer hollow cylindrical fiber cladding 18. The refractive index of the fiber core 17 is greater than the refractive index of the fiber cladding 18, so that the light fed into the fiber core 17 is predominantly totally reflected at the fiber cladding 18.

The fiber optic sensor 11, 25 is designed here as a fiber Bragg grating sensor, for example. Accordingly, several fiber Bragg gratings 19 arranged at equal distances from one another are formed in the optical waveguide 15, 26. The light radiated by the light source 13 into the fiber core 17 generates an interference pattern on the fiber Bragg grating 19. The radiated light signal has 4a a homogeneous input spectrum 21. A portion of the light is transmitted through the fiber Bragg grating 19 and has a 4b A further portion of the light is reflected by the fiber Bragg grating 19 and thereby generates the 4c shown reflection spectrum 22.

In the present example, the reflection spectrum 22 is received as an output signal of the fiber optic sensor 11, 25 by the light detector 14 and evaluated in the optoelectronic control unit 12, 27. If the optical waveguide 15, 26 is deformed due to coupling forces or axle loads, the period of the grating spacing of the fiber Bragg grating 19 changes. As a result, the received reflection spectrum 22 is shifted in wavelength. The degree of deformation of the optical waveguide 15, 26 can be determined from a continuous so-called pattern comparison between the radiated input spectrum 21 and the received reflection spectrum 22. In a further process step, these deformation values are correlated with the causal coupling force or axle load, for example using the finite element method. From this, the amount and direction of the coupling force acting on the coupling device are determined, and these values are then passed on to the vehicle control unit 29, where these values are then available for further processing.

It should be noted again that the design of the fiber optic sensor 11, 25 as a fiber Bragg sensor is only to be understood as an example. It should be pointed out in particular that for an alternative evaluation of coupling force-related or axle load-related changes in the light propagation in an optical fiber, the various types of light scattering described above can be used, by means of which both forces and moments as well as temperature influences and/or vibration influences which act on the coupling device 6 of the vehicle combination 1 can be selectively analyzed.

Reference symbol (part of the description)

1

Vehicle combination

2

towing vehicle, tractor, tractor

3

Trailer vehicle

4

Vehicle transmission

5

Vehicle wheel axle, rear axle of the towing vehicle

5a

First axle trumpet of the rear axle

5b

Second axle trumpet of the rear axle

6

Coupling device on the towing vehicle

7

Vehicle gearbox housing

10a

Measuring device (1st embodiment)

10b

Measuring device (2nd embodiment)

11

Fiber optic sensor (1st embodiment)

12

Optoelectronic control unit (1st embodiment)

13

Light source

14

Light detector

15

Optical fiber (1st embodiment)

16

Optocoupler

17

Fiber core of the optical fiber

18

Fiber cladding of the optical fiber

19

Fiber Bragg Grating

20

Transmission spectrum of the output signal

21

Input spectrum of the light signal

22

Reflection spectrum of the output signal

25

Fiber optic sensor (2nd embodiment)

26

Optical fiber (2nd embodiment)

27

Optoelectronic control unit (2nd embodiment)

28

Sensor cable

29

Vehicle control unit

30

Energy source

31

Electrical line

λ

Wavelength of Rayleigh scattering

λ_0

Wavelength of the incident light signal

Fx, Fy, Fz

Components of a coupling force

I

Intensity of the Rayleigh scattering signal

T

temperature

ε

strain

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely to provide the reader with better information. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102018106855 A1 [0004]
• DE 102019124281 A1 [0005]
• EP 2366563 A2 [0007]
• EP 1421355 B1 [0009]

Claims (11)

Measuring device (10a) for measuring forces acting on a vehicle combination (1), the vehicle combination (1) consisting of a towing vehicle, tractor (2) or a tractor with a coupling device (6) and a trailer (3) coupled thereto or an attachment coupled thereto, characterized in that a fiber optic sensor (11) is arranged on the housing (7) of a vehicle transmission (4) of the towing vehicle, tractor (2) or tractor in such a way that it also deforms when the housing (7) of the vehicle transmission (4) is mechanically deformed and in the process changes its optical properties, that the sensor (11) has an optoelectronic control unit (12) for generating and processing an optical output signal (20, 22), that a computer program is stored in the control unit (12), by means of which a coupling force acting on the coupling device (6) can be determined by evaluating the optical output signal (20, 22), and that an electrical signal representing the measured coupling force can be generated by means of the control unit (12) and sent to a vehicle control unit (29). Measuring device (10b) for measuring forces acting on a vehicle combination (1), the vehicle combination (1) consisting of a towing vehicle, tractor (2) or a tractor with a coupling device (6) and a trailer (3) coupled thereto or an attachment coupled thereto, characterized in that a fiber optic sensor (25) is arranged on at least one axle trumpet (5a, 5b) of a vehicle wheel axle (5) of the towing vehicle, the tractor (2) or the tractor in such a way that it also deforms when the axle trumpet (5a, 5b) is mechanically deformed and in the process changes its optical properties, that the sensor (25) has an optoelectronic control unit (27) for generating and processing an optical output signal (20, 22), that a computer program is stored in the control unit (27), by means of which a force acting on the coupling device (6) can be determined by evaluating the optical output signal (20, 22). Coupling force can be determined, and that by means of the control unit (27) an electrical signal representing the measured coupling force can be generated and sent to a vehicle control unit (29). Measuring device (10a, 10b) according to Claim 1 or Claim 2 , characterized in that the fiber optic sensor (11) has at least one optical waveguide (15) connected to the optoelectronic control unit (12), that the control unit (12) has a light source (13) and a light detector (14), that the light source (13) is designed and arranged to emit a light signal (21) propagating in the optical waveguide (15), and that the light detector (14) is designed to detect and optically-electrically convert an output signal (20, 22) of the light signal (21) reflected back into the light detector (14) via the optical waveguide (15), or transmitted through the optical waveguide (15), or fed to the light detector (14) via an additional optical signal line. Measuring device according to Claim 3 , characterized in that the fiber optic sensor (25) is arranged on the inside of one or two axle trumpets (5a, 5b) of a rear vehicle wheel axle (5) of the towing vehicle, the tractor (2) or the tractor. Measuring device according to one of the Claims 1 until 4 , characterized in that the fiber optic sensor (11, 25) has the functionality of a fiber Bragg grating sensor, wherein at least two fiber Bragg gratings (19) are arranged in the optical waveguide (15, 26). Measuring device according to one of the Claims 1 until 4 , characterized in that the fiber optic sensor (11, 25) has the functionality of a Raman sensor. Measuring device according to one of the Claims 1 until 4 , characterized in that the fiber optic sensor (11, 25) has the functionality of a Brillouin sensor. Measuring device according to one of the Claims 1 until 4 , characterized in that the fiber optic sensor (11, 25) has the functionality of a Rayleigh sensor. Method for measuring coupling forces and/or axle loads on a vehicle combination (1) consisting of a towing vehicle, a tractor (2) or a tractor and a trailer vehicle (3) coupled thereto or an attachment coupled thereto, by means of a measuring device (10a, 10b) with the features of at least one of the device claims, characterized in that that an output signal (20, 22) received by the light detector (14) is evaluated by the optoelectronic control unit (12, 27) by means of a spectral pattern comparison between light signal parameters emitted by the light source (13) and detected by the light detector (14), continuously or repeatedly at time intervals, the intensity, phase, wavelength and/or polarization of the light being used as light signal parameters, that the degree of deformation of the optical waveguide (15, 26) is determined by means of the evaluation of the output signal (20, 22), that a value of a coupling force and/or axle load causing this is calculated from the deformation of the optical waveguide (15, 26) using a numerical calculation method, and that the calculated coupling force value and/or axle load value is made available as a sensor signal for further processing. Computer program for determining coupling forces and/or axle loads on a vehicle combination (1) consisting of a towing vehicle, a tractor (2) or a tractor and a trailer vehicle (3) coupled thereto or an attachment coupled thereto, wherein the computer program is designed in such a way that the method of the independent method claim can be operated with it. Vehicle combination (1) comprising a towing vehicle, a tractor (2) or a tractor with an attachment and/or at least one trailer vehicle (3), with a measuring device (10a, 10b) which is constructed according to at least one of the device claims and can be operated to carry out a method according to the method claim.

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